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    <title>Document</title>
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    <script>

        /* 
         - 基本数据类型

         - string    typeof 'string'
         - number    typeof 'number'
         - boolean   typeof 'boolean'
         - undefined typeof 'undefined'
         - null      typeof 'object'

         - 复杂数据类型

         - Object     intanceof  Object
         - function   intanceof  Funtion /   typeof 'function'
         - Array    intanceof  Array     

         * 如何判断
         - typeof      判断简单数据类型    
         - instanceof  instance 实例  左边是否是右边的实例
         - ===
        */

        let h = false
        let z= undefined
        let k = null
        let a =2
        let b= {}
        let c = []
        let d = function(){}
        console.log( d instanceof Function);
    </script>
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